When to Perform an ECG in Adults with Cardiovascular Symptoms
An ECG should be performed immediately—within 10 minutes of presentation—for any adult patient presenting with chest pain, shortness of breath, or other symptoms suggestive of cardiovascular disease. This is a Class I recommendation that applies regardless of the patient's baseline risk profile 1, 2.
Immediate ECG Indications (Class I - Must Perform)
The following symptoms mandate immediate ECG acquisition 1, 2:
- Chest pain or anginal equivalent - Any quality of chest discomfort warrants immediate ECG to rule out acute coronary syndrome 1, 3
- Dyspnea (shortness of breath) - New or worsening dyspnea requires ECG evaluation 1, 3
- Syncope or near-syncope - Loss of consciousness or near-fainting episodes necessitate immediate ECG 1, 2
- Palpitations - Sensation of irregular or rapid heartbeat requires rhythm assessment 1, 3
- Extreme unexplained fatigue, weakness, or prostration - These may represent cardiac decompensation 1
Critical Timing Considerations
The ECG must be performed and interpreted by an experienced physician within 10 minutes of emergency department arrival for patients with chest pain or other acute coronary syndrome symptoms 1. This timing is essential because:
- Acute myocardial infarction requires immediate identification for reperfusion therapy 1
- Door-to-fibrinolysis time of ≤30 minutes significantly reduces mortality in STEMI patients 1
- Early ECG changes may be transient and missed with delayed acquisition 4
Risk Stratification Based on Initial ECG
Once obtained, the ECG provides powerful prognostic information 5:
- Normal ECG with upright T waves and isoelectric ST segments: Only 1-4% of these patients have acute MI, representing extremely low risk 4, 5
- Nonspecific ST-T wave abnormalities: Approximately 4% incidence of MI, requiring clinical correlation 4
- ST segment elevation or depression: 54% of these patients have acute MI and require immediate hospital admission 5
Important Clinical Caveat
A normal or nonspecific ECG does NOT rule out acute myocardial infarction. The ECG is diagnostic of AMI in only 50% of patients at initial evaluation 4. The clinical history remains the most important diagnostic tool, and overreliance on a normal ECG in a patient with classic anginal symptoms is dangerous 4, 3. Serial ECGs and cardiac biomarkers are essential when clinical suspicion remains high despite an initially normal ECG 4.
Additional Indications for ECG in Symptomatic Patients
Beyond acute presentations, ECG is indicated for 1:
- Unexplained change in usual pattern of angina - Suggests unstable angina or progression of disease 1
- Patients with known cardiovascular disease experiencing symptom changes - Any change in clinical status warrants repeat ECG 1
- Suspected cardiac arrhythmias - ECG is the only practical noninvasive method for documenting rhythm disturbances 1
What NOT to Do
Do not perform screening ECGs in asymptomatic adults at low cardiovascular risk 1, 6. For asymptomatic patients without symptoms or risk factors, screening ECG provides no benefit and may lead to false-positive results causing unnecessary invasive testing, radiation exposure, and potential harm from unwarranted procedures 1, 6.